Los Angeles County may not be the first place you think of in the context of bicycle transportation. I imagine the freeways that chop the infrastructure into little pieces are a major obstacle. But the weather is certainly agreeable, and lots of people ride bikes, even in such an unlikely, car-centric place.
Lots of bikes - lots of crashes. In 2012, the authorities documented 5090 crashes involving a bicycle and a car.
What can we learn from the statistics?
1) Cyclists were more likely to be at fault, according to the authorities. (Nationwide in such crashes, the fault is pretty evenly divided between the cyclist and the motorist.)
2) In the 1878 crashes that were determined to be the fault of the motorist, failure to yield was the most frequent behavior leading to a collision. Second was improper turning. Other causes - disobeying traffic signals, "other hazardous violation," and excessive speed. No surprise there.
3) In the 2759 crashes that were caused by the cyclist's behavior... the #1 behavior by a wide margin was "biking on the wrong side of the road." (Others, but small percentages: failure to yield, disobeying traffic signals, improper turning.) No surprise? Unfortunately, it's unlikely that this sort of empirical information will make much of a difference... against-traffic riding laws are rarely enforced unless a crash is involved, and the against-traffic riders seem perfectly content to expose themselves to additional risk, riding along in blissful ignorance.